1. Field of the Invention
The present invention is directed to alarm systems for motor vehicles which are placed within the cab area of the vehicle so as to set off an alarm to warn of imminent intrusion. More specifically, the present invention is directed to a motor vehicle alarm system which is responsive to the intrusion of light and particularly to the shining of a flashlight, e.g. of a thief, into the dashboard area of a motor vehicle such as occurs when a thief is examining a vehicle prior to entry to determine whether or not there is a valuable, accessible stereo system, radar detector or the like.
2. Prior Art Statement
The prior art is replete with patent references which show various types of alarm systems to warn of intrusion by thieves of motor vehicles or thieves who intend to take components from inside the motor vehicles. Most of these alarms involve responsive detection of tampering, vibrations or removal or opening of windows, doors, hoods, trunks or the like. Typical of these prior art references are U.S. Pat. Nos. 3,986,166 which is issued to Michel Kohn; 4,052,716 issued to Tage Mortensen; and, 4,638,293 issued to Byung-Woo Min. These three patents span the past decade or so and are typical of the state of the art.
U.S. Pat. No. 3,986,166 is directed to an alarm system for automobiles which is actuated when an unauthorized person tampers with the automobile. In this particular invention, an inductive coupling is made with the automobile electrical system so that a variation in current flow in the system activates the alarm. Provision is made for the operator to turn on and off the system.
U.S. Pat. No. 4,052,716 is directed to a device for monitoring an area under surveillance for detecting the existence of a fire, the presence of an intruder or the occurrence of other abnormal conditions, as well as a warning signal for actuating an alarm in response thereto. The particular device employs a plurality of sensors which respond by changes in the electrical characteristics thereof to the level of infrared, light or other radiations from the monitored space respectively sensed thereby. In other words, the device reacts to interference by smoke, fire or an intruder and sets off an alarm. An elaborate electrical schematic diagram is shown which involves various types of sensors to signal alarms in response to predetermined conditions.
U.S. Pat. No. 4,638,293 issued on Jan. 20, 1987 is directed to an alarm system for an automobile comprising an alarm circuit chip which is built into the car stereo housing and interfaced with the stereo circuitry. In this invention, the alarm system is controlled and programmed by the same selector buttons and controls which are used in conjunction with the car stereo and radio. Some of the sensors for the alarm system are disposed in conventional circuit portions of the car, such as the door, hood and trunk light circuits.
Some prior art systems focus specifically on methods and apparatus for detecting changes in lighting intensity utilizing a microprocessor, as set forth in U.S. Pat. No. 4,460,892 and photosensitive alarm systems as set forth in U.S. Pat. No. 4,242,670. These patents show specific variations on the concept of measuring and electronically reacting to light changes so as to set off an alarm signal.
While all of the above cited patents are exemplary of the prior art relating to automobile alarm systems or to the prior art of alarm systems in general, it should be noted that none of these references describe or suggest the present invention alarm system which is adapted to respond to the intrusion of light. Although U.S. Pat. No. 4,638,293 issued only months prior to this application, and many types of alarm systems are described therein, there is no indication of any system which would be responsive to the intrusion of flashlight or other lighting by a potential thief. Thus, the particularly advantageous system of signalling an alarm before a potential intruder physically breaks a window or door lock is not set forth in the prior art whereas it is the essential feature of the present invention.